Culvert pipes, which are widely used to allow water to flow beneath roads without having to redirect it or construct a bridge to pass over the water, present an ideal place for beavers to construct a dam and restrict the flow of water. A number of previous patents have sought to deal with this problem, in which they prevent beavers from entering culvert pipes by physically obstructing an entrance at an end of the culvert pipe through the use of screens. In addition to deterring beavers from entering culvert pipes, it is important to deter them from building dams that obstruct the flow of water through the culvert pipe, too. For example, U.S. Pat. Nos. 5,102,537; 6,447,206; and 7,441,989 describe cone-shaped screens that block beavers and similarly-sized animals from entering the culvert pipe. Furthermore, the cone-shaped screens deter beavers from constructing dams as the beavers are unable to properly anchor the dam. In spite of these benefits, screen-based beaver control devices have shortcomings. Firstly, the small debris may still gather at the screen and promote clogging of the entrance of the culvert pipe. Furthermore, these screens inhibit passage of fish and turtles through the culvert pipe.